Electronic device air-cavity packages include a base and a lid, which together define an enclosed interior cavity within which various types of electronic die may be attached. In some types of packages, the base comprises a die pad (or “flag”) surrounded by a plurality of leads, where the combination is structurally supported by molding compound. Typically, manufacturing the base involves providing a leadframe (i.e., a conductive structure that includes one or more instances of the die pad/lead combination, held in spatial orientation by sacrificial features), placing the leadframe in a mold, and surrounding side surfaces of the die pad and leads with the molding compound so that top and bottom surfaces of the die pad and leads are exposed.
During the device assembly process, one or more dies are attached to the die pad, electrical connections are established between the die and the leads (e.g., using wirebonds and/or other conductive features), and the lid is attached to the base. When a lid is to be permanently attached to the base, a heat-curably epoxy is typically applied to the mating surface of the lid and/or base, and the assembly is cured at an elevated temperature (e.g., between about 150° C. to 175° C.) for a cure period (e.g., about an hour). To allow for pressure normalization between the air cavity and the external environment during the lid cure process, one or more vent holes are typically provided in the assembly prior to the process. The holes may be later sealed to hermetically or semi-hermetically seal the air cavity, although the holes may be left open, in some packages.
Although provision of vent holes reduces the likelihood that the seal between the base and the lid may rupture during the lid attach process (e.g., due to differential pressures between the air cavity and outside environment), the use of such holes is not without its issues. For example, debris from the outside environment may enter the air cavity through the vent holes when they are unsealed, and this debris could short exposed wirebonds or other conductive features within the air cavity. Accordingly, although the use of vent holes alleviates some manufacturing issues, the vent holes cause other issues.